/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;
using org.apache.commons.collections.functors;

namespace org.apache.commons.collections
{

    /**
     * <code>TransformerUtils</code> provides reference implementations and 
     * utilities for the Transformer functor interface. The supplied transformers are:
     * <ul>
     * <li>Invoker - returns the result of a method call on the input object
     * <li>Clone - returns a clone of the input object
     * <li>Constant - always returns the same object
     * <li>Closure - performs a Closure and returns the input object
     * <li>Predicate - returns the result of the predicate as a Boolean
     * <li>Factory - returns a new object from a factory
     * <li>Chained - chains two or more transformers together
     * <li>Switch - calls one transformer based on one or more predicates
     * <li>SwitchMap - calls one transformer looked up from a Map
     * <li>Instantiate - the Class input object is instantiated
     * <li>Map - returns an object from a supplied Map
     * <li>Null - always returns null
     * <li>NOP - returns the input object, which should be immutable
     * <li>Exception - always throws an exception
     * <li>StringValue - returns a <code>java.lang.String</code> representation of the input object
     * </ul>
     * All the supplied transformers are Serializable.
     *
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     * 
     * @author Stephen Colebourne
     * @author James Carman
     */
    public class TransformerUtils
    {

        /**
         * This class is not normally instantiated.
         */
        public TransformerUtils()
            : base()
        {
        }

        /**
         * Gets a transformer that always throws an exception.
         * This could be useful during testing as a placeholder.
         * 
         * @see org.apache.commons.collections.functors.ExceptionTransformer
         * 
         * @return the transformer
         */
        public static Transformer exceptionTransformer()
        {
            return ExceptionTransformer.INSTANCE;
        }

        /**
         * Gets a transformer that always returns null.
         * 
         * @see org.apache.commons.collections.functors.ConstantTransformer
         * 
         * @return the transformer
         */
        public static Transformer nullTransformer()
        {
            return ConstantTransformer.NULL_INSTANCE;
        }

        /**
         * Gets a transformer that returns the input object.
         * The input object should be immutable to maintain the
         * contract of Transformer (although this is not checked).
         * 
         * @see org.apache.commons.collections.functors.NOPTransformer
         * 
         * @return the transformer
         */
        public static Transformer nopTransformer()
        {
            return NOPTransformer.INSTANCE;
        }

        /**
         * Gets a transformer that returns a clone of the input
         * object. The input object will be cloned using one of these
         * techniques (in order):
         * <ul>
         * <li>public clone method
         * <li>public copy constructor
         * <li>serialization clone
         * <ul>
         * 
         * @see org.apache.commons.collections.functors.CloneTransformer
         * 
         * @return the transformer
         */
        public static Transformer cloneTransformer()
        {
            return CloneTransformer.INSTANCE;
        }

        /**
         * Creates a Transformer that will return the same object each time the 
         * transformer is used.
         *
         * @see org.apache.commons.collections.functors.ConstantTransformer
         * 
         * @param constantToReturn  the constant object to return each time in the transformer
         * @return the transformer.
         */
        public static Transformer constantTransformer(Object constantToReturn)
        {
            return ConstantTransformer.getInstance(constantToReturn);
        }

        /**
         * Creates a Transformer that calls a Closure each time the transformer is used.
         * The transformer returns the input object.
         *
         * @see org.apache.commons.collections.functors.ClosureTransformer
         * 
         * @param closure  the closure to run each time in the transformer, not null
         * @return the transformer
         * @throws IllegalArgumentException if the closure is null
         */
        public static Transformer asTransformer(Closure closure)
        {
            return ClosureTransformer.getInstance(closure);
        }

        /**
         * Creates a Transformer that calls a Predicate each time the transformer is used.
         * The transformer will return either Boolean.TRUE or Boolean.FALSE.
         *
         * @see org.apache.commons.collections.functors.PredicateTransformer
         * 
         * @param predicate  the predicate to run each time in the transformer, not null
         * @return the transformer
         * @throws IllegalArgumentException if the predicate is null
         */
        public static Transformer asTransformer(Predicate predicate)
        {
            return PredicateTransformer.getInstance(predicate);
        }

        /**
         * Creates a Transformer that calls a Factory each time the transformer is used.
         * The transformer will return the value returned by the factory.
         *
         * @see org.apache.commons.collections.functors.FactoryTransformer
         * 
         * @param factory  the factory to run each time in the transformer, not null
         * @return the transformer
         * @throws IllegalArgumentException if the factory is null
         */
        public static Transformer asTransformer(Factory factory)
        {
            return FactoryTransformer.getInstance(factory);
        }

        /**
         * Create a new Transformer that calls two transformers, passing the result of
         * the first into the second.
         * 
         * @see org.apache.commons.collections.functors.ChainedTransformer
         * 
         * @param transformer1  the first transformer
         * @param transformer2  the second transformer
         * @return the transformer
         * @throws IllegalArgumentException if either transformer is null
         */
        public static Transformer chainedTransformer(Transformer transformer1, Transformer transformer2)
        {
            return ChainedTransformer.getInstance(transformer1, transformer2);
        }

        /**
         * Create a new Transformer that calls each transformer in turn, passing the 
         * result into the next transformer.
         * 
         * @see org.apache.commons.collections.functors.ChainedTransformer
         * 
         * @param transformers  an array of transformers to chain
         * @return the transformer
         * @throws IllegalArgumentException if the transformers array is null
         * @throws IllegalArgumentException if any transformer in the array is null
         */
        public static Transformer chainedTransformer(Transformer[] transformers)
        {
            return ChainedTransformer.getInstance(transformers);
        }

        /**
         * Create a new Transformer that calls each transformer in turn, passing the 
         * result into the next transformer. The ordering is that of the iterator()
         * method on the collection.
         * 
         * @see org.apache.commons.collections.functors.ChainedTransformer
         * 
         * @param transformers  a collection of transformers to chain
         * @return the transformer
         * @throws IllegalArgumentException if the transformers collection is null
         * @throws IllegalArgumentException if any transformer in the collection is null
         */
        public static Transformer chainedTransformer(java.util.Collection<Object> transformers)
        {
            return ChainedTransformer.getInstance(transformers);
        }

        /**
         * Create a new Transformer that calls one of two transformers depending 
         * on the specified predicate.
         * 
         * @see org.apache.commons.collections.functors.SwitchTransformer
         * 
         * @param predicate  the predicate to switch on
         * @param trueTransformer  the transformer called if the predicate is true
         * @param falseTransformer  the transformer called if the predicate is false
         * @return the transformer
         * @throws IllegalArgumentException if the predicate is null
         * @throws IllegalArgumentException if either transformer is null
         */
        public static Transformer switchTransformer(Predicate predicate, Transformer trueTransformer, Transformer falseTransformer)
        {
            return SwitchTransformer.getInstance(new Predicate[] { predicate }, new Transformer[] { trueTransformer }, falseTransformer);
        }

        /**
         * Create a new Transformer that calls one of the transformers depending 
         * on the predicates. The transformer at array location 0 is called if the
         * predicate at array location 0 returned true. Each predicate is evaluated
         * until one returns true. If no predicates evaluate to true, null is returned.
         * 
         * @see org.apache.commons.collections.functors.SwitchTransformer
         * 
         * @param predicates  an array of predicates to check
         * @param transformers  an array of transformers to call
         * @return the transformer
         * @throws IllegalArgumentException if the either array is null
         * @throws IllegalArgumentException if the either array has 0 elements
         * @throws IllegalArgumentException if any element in the arrays is null
         * @throws IllegalArgumentException if the arrays are different sizes
         */
        public static Transformer switchTransformer(Predicate[] predicates, Transformer[] transformers)
        {
            return SwitchTransformer.getInstance(predicates, transformers, null);
        }

        /**
         * Create a new Transformer that calls one of the transformers depending 
         * on the predicates. The transformer at array location 0 is called if the
         * predicate at array location 0 returned true. Each predicate is evaluated
         * until one returns true. If no predicates evaluate to true, the default
         * transformer is called. If the default transformer is null, null is returned.
         * 
         * @see org.apache.commons.collections.functors.SwitchTransformer
         * 
         * @param predicates  an array of predicates to check
         * @param transformers  an array of transformers to call
         * @param defaultTransformer  the default to call if no predicate matches, null means return null
         * @return the transformer
         * @throws IllegalArgumentException if the either array is null
         * @throws IllegalArgumentException if the either array has 0 elements
         * @throws IllegalArgumentException if any element in the arrays is null
         * @throws IllegalArgumentException if the arrays are different sizes
         */
        public static Transformer switchTransformer(Predicate[] predicates, Transformer[] transformers, Transformer defaultTransformer)
        {
            return SwitchTransformer.getInstance(predicates, transformers, defaultTransformer);
        }

        /**
         * Create a new Transformer that calls one of the transformers depending 
         * on the predicates. 
         * <p>
         * The Map consists of Predicate keys and Transformer values. A transformer 
         * is called if its matching predicate returns true. Each predicate is evaluated
         * until one returns true. If no predicates evaluate to true, the default
         * transformer is called. The default transformer is set in the map with a 
         * null key. If no default transformer is set, null will be returned in a default
         * case. The ordering is that of the iterator() method on the entryset collection 
         * of the map.
         * 
         * @see org.apache.commons.collections.functors.SwitchTransformer
         * 
         * @param predicatesAndTransformers  a map of predicates to transformers
         * @return the transformer
         * @throws IllegalArgumentException if the map is null
         * @throws IllegalArgumentException if the map is empty
         * @throws IllegalArgumentException if any transformer in the map is null
         * @throws ClassCastException  if the map elements are of the wrong type
         */
        public static Transformer switchTransformer(java.util.Map<Object, Object> predicatesAndTransformers)
        {
            return SwitchTransformer.getInstance(predicatesAndTransformers);
        }

        /**
         * Create a new Transformer that uses the input object as a key to find the
         * transformer to call. 
         * <p>
         * The Map consists of object keys and Transformer values. A transformer 
         * is called if the input object equals the key. If there is no match, the
         * default transformer is called. The default transformer is set in the map
         * using a null key. If no default is set, null will be returned in a default case.
         * 
         * @see org.apache.commons.collections.functors.SwitchTransformer
         * 
         * @param objectsAndTransformers  a map of objects to transformers
         * @return the transformer
         * @throws IllegalArgumentException if the map is null
         * @throws IllegalArgumentException if the map is empty
         * @throws IllegalArgumentException if any transformer in the map is null
         */
        public static Transformer switchMapTransformer(java.util.Map<Object, Object> objectsAndTransformers)
        {
            Transformer[] trs = null;
            Predicate[] preds = null;
            if (objectsAndTransformers == null)
            {
                throw new java.lang.IllegalArgumentException("The object and transformer map must not be null");
            }
            Transformer def = (Transformer)objectsAndTransformers.remove(null);
            int size = objectsAndTransformers.size();
            trs = new Transformer[size];
            preds = new Predicate[size];
            int i = 0;
            for (java.util.Iterator<java.util.MapNS.Entry<Object, Object>> it = objectsAndTransformers.entrySet().iterator(); it.hasNext(); )
            {
                java.util.MapNS.Entry<Object, Object> entry = (java.util.MapNS.Entry<Object, Object>)it.next();
                preds[i] = EqualPredicate.getInstance(entry.getKey());
                trs[i] = (Transformer)entry.getValue();
                i++;
            }
            return switchTransformer(preds, trs, def);
        }

        /**
         * Gets a Transformer that expects an input Class object that it will instantiate.
         * 
         * @see org.apache.commons.collections.functors.InstantiateTransformer
         * 
         * @return the transformer
         */
        public static Transformer instantiateTransformer()
        {
            return InstantiateTransformer.NO_ARG_INSTANCE;
        }

        /** 
         * Creates a Transformer that expects an input Class object that it will 
         * instantiate. The constructor used is determined by the arguments specified
         * to this method.
         *
         * @see org.apache.commons.collections.functors.InstantiateTransformer
         * 
         * @param paramTypes  parameter types for the constructor, can be null
         * @param args  the arguments to pass to the constructor, can be null
         * @return the transformer
         * @throws IllegalArgumentException if the paramTypes and args don't match
         */
        public static Transformer instantiateTransformer(java.lang.Class[] paramTypes, Object[] args)
        {
            System.Type[] types = new System.Type[paramTypes.Length];
            for (int i = 0; i < paramTypes.Length; i++)
            {
                types[i] = paramTypes[i].getDelegateInstance();
            }
            return InstantiateTransformer.getInstance(paramTypes, args);
        }

        /** 
             * Creates a Transformer that uses the passed in Map to transform the input 
             * object (as a simple lookup).
             *
             * @see org.apache.commons.collections.functors.MapTransformer
             * 
             * @param map  the map to use to transform the objects
             * @return the transformer
             * @throws IllegalArgumentException if the map is null
             */
        public static Transformer mapTransformer(java.util.Map<Object, Object> map)
        {
            return MapTransformer.getInstance(map);
        }

        /**
         * Gets a Transformer that invokes a method on the input object.
         * The method must have no parameters. If the input object is null, 
         * null is returned.
         * <p>
         * For example, <code>TransformerUtils.invokerTransformer("getName");</code>
         * will call the <code>getName/code> method on the input object to 
         * determine the transformer result.
         * 
         * @see org.apache.commons.collections.functors.InvokerTransformer
         * 
         * @param methodName  the method name to call on the input object, may not be null
         * @return the transformer
         * @throws IllegalArgumentException if the methodName is null.
         */
        public static Transformer invokerTransformer(String methodName)
        {
            return InvokerTransformer.getInstance(methodName, (java.lang.Class[])null, null);
        }

        /**
         * Gets a Transformer that invokes a method on the input object.
         * The method parameters are specified. If the input object is null, 
         * null is returned.
         * 
         * @see org.apache.commons.collections.functors.InvokerTransformer
         * 
         * @param methodName  the name of the method
         * @param paramTypes  the parameter types
         * @param args  the arguments
         * @return the transformer
         * @throws IllegalArgumentException if the method name is null
         * @throws IllegalArgumentException if the paramTypes and args don't match
         */
        public static Transformer invokerTransformer(String methodName, java.lang.Class[] paramTypes, Object[] args)
        {
            System.Type[] types = new System.Type[paramTypes.Length];
            for (int i = 0; i < paramTypes.Length; i++)
            {
                types[i] = paramTypes[i].getDelegateInstance();
            }
            return invokerTransformer(methodName, types, args);
        }
        /// <summary>
        /// In addition, you can use native System.Type param...
        /// </summary>
        /// <param name="methodName"></param>
        /// <param name="paramTypes"></param>
        /// <param name="args"></param>
        /// <returns></returns>
        public static Transformer invokerTransformer(String methodName, System.Type[] paramTypes, Object[] args)
        {
            return InvokerTransformer.getInstance(methodName, paramTypes, args);
        }

        /**
         * Gets a transformer that returns a <code>java.lang.String</code>
         * representation of the input object. This is achieved via the
         * <code>toString</code> method, <code>null</code> returns 'null'.
         * 
         * @see org.apache.commons.collections.functors.StringValueTransformer
         * 
         * @return the transformer
         */
        public static Transformer stringValueTransformer()
        {
            return StringValueTransformer.INSTANCE;
        }

    }
}